If you need to maintain a large piece of software written in Perl by other people in the last 5-10-15 years,
that's a challenge. Especially if you did not get proper training in Perl. You are probably limited to
a specific and old version of Perl. Check out, the Perl tutorial!
You can probably skip the part about installing Perl, but the rest of the tutorial will be relevant for you.

Perl is often used in Test Automation. If you work in this field, or if you'd like to work in this field
(it is much more fun to find bugs in other people's code than in yours :), then you can read the Perl tutorial
and the series on Test Automation using Perl.